:root {
  --bg: #ffffff;
  --surface: #f4f4f5;
  --border: #e4e4e7;
  --text: #18181b;
  --text-muted: #71717a;
  --header-bg: #18181b;
  --header-text: #ffffff;
  --accent: #6366f1;
  --accent-hover: #4f46e5;
  --card-bg: #ffffff;
  --shadow: 0 1px 3px rgba(0,0,0,0.08), 0 1px 2px rgba(0,0,0,0.06);
}

[data-theme="dark"] {
  --bg: #09090b;
  --surface: #18181b;
  --border: #27272a;
  --text: #fafafa;
  --text-muted: #a1a1aa;
  --header-bg: #09090b;
  --header-text: #fafafa;
  --accent: #818cf8;
  --accent-hover: #6366f1;
  --card-bg: #18181b;
  --shadow: 0 1px 3px rgba(0,0,0,0.4), 0 1px 2px rgba(0,0,0,0.3);
}

*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  transition: background 0.2s, color 0.2s;
}

/* Header */
header {
  background: var(--header-bg);
  color: var(--header-text);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 1.5rem;
  height: 56px;
  display: flex;
  align-items: center;
  gap: 1.5rem;
}

.logo {
  font-weight: 700;
  font-size: 1.15rem;
  letter-spacing: -0.01em;
  color: var(--header-text);
  flex-shrink: 0;
}

nav {
  display: flex;
  gap: 0.25rem;
  flex: 1;
}

nav a {
  color: #a1a1aa;
  text-decoration: none;
  font-size: 0.9rem;
  padding: 0.35rem 0.7rem;
  border-radius: 6px;
  transition: color 0.15s, background 0.15s;
}

nav a:hover {
  color: #ffffff;
  background: rgba(255,255,255,0.08);
}

/* Dark mode toggle */
.dark-mode-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 8px;
  border: 1px solid rgba(255,255,255,0.15);
  background: rgba(255,255,255,0.06);
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s;
  flex-shrink: 0;
  font-size: 1rem;
  line-height: 1;
}

.dark-mode-toggle:hover {
  background: rgba(255,255,255,0.12);
  border-color: rgba(255,255,255,0.25);
}

.dark-mode-toggle:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

/* Show sun in dark mode, moon in light mode */
.icon-sun { display: none; }
.icon-moon { display: block; }

[data-theme="dark"] .icon-sun { display: block; }
[data-theme="dark"] .icon-moon { display: none; }

/* Main content */
main {
  max-width: 1100px;
  margin: 0 auto;
  padding: 3rem 1.5rem;
}

.hero {
  text-align: center;
  padding: 3rem 0 2.5rem;
}

.hero h1 {
  font-size: clamp(1.75rem, 4vw, 2.75rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  margin-bottom: 0.75rem;
}

.hero p {
  font-size: 1.1rem;
  color: var(--text-muted);
}

/* Cards */
.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.25rem;
  margin-top: 2.5rem;
}

.card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
  box-shadow: var(--shadow);
  transition: background 0.2s, border-color 0.2s, box-shadow 0.2s;
}

.card h2 {
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}

.card p {
  font-size: 0.9rem;
  color: var(--text-muted);
}

/* Footer */
footer {
  border-top: 1px solid var(--border);
  padding: 1.5rem;
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-muted);
}